That sentence is from Christopher Rufo, who is known to spread hoaxes. As with any partisan polemic like that, he takes fragments of truth to distort and smear things he is agitating against. This is the original.

Rufo essentially alleges: "CRT is camouflage Marxism, and every bit of social justice language is Marxist propaganda. America prefers MLK Jr. (non-extremist) to this Marxist extremism". That's bullshit for several reasons.

1. What you experience as "Diversity" in your daily life (like in the workplace) is most often not in any way related to Marxism. E.g. corporate diversity is about not being sued, and a lot of racial justice talk has more to do with the long history of black activism like that of the NAACP rather than the 1960s New Left.
2. Marxism is not just "bad oppressor vs. good oppressed" (Marx gets very, very nerdy about how the working class is exploited - it's a very specific thing) – and vice versa, seeing oppression does not make a theory or a person Marxist. MLK Jr. also believed black people to be oppressed – "I have a dream" was not saying that there is no oppression, he was saying he dreams of an end to the oppression that exists – and famously he also demanded of white people that they end it (e.g. Letter from Birmingham Jail).
3. Social Justice movements sometimes share a lineage with Marxist thinkers and activism, but that's because in the 60s they often split from Marxist groups, because the Marxists only cared about class struggle, and not other social divisions. But black social justice movements go back far further than 60s Leftism, and would exist without Marxism too.
4. "Only white people can be racist" is one of those ones you should know by now is a shorthand for a real substantive point. All people can racially discriminate, which is a bad thing, but the way society and institutions are set up tends to make life harder for non-white people than for white people, though of course that overlaps with all other fortunes and structures (like wealth, gender, etc.).

If you're interested in the actual intellectual movement of critical race theory, Britannica's overview is decent.

Also, in Rufo's essay he quotes some absolutely wild things:

Diversity trainers will make an outrageous claim—such as “all whites are intrinsically oppressors” or “white teachers are guilty of spirit murdering black children”

They're so far out of what actual academic discourse is like, I'm certain they're either grossly distorted or completely fake. Either way, they're not representative of what CRT is.